Apparatus and process for measuring properties

Abstract

The present invention relates to an apparatus and process for measuring a property of a material such as the moisture content of cotton fiber. An embodiment is specifically adapted for determining an absolute value of the moisture content of the cotton fiber while being conveyed through ducts such as the ducts of the ginning machine. The embodiment combines large area capacitor plates with light detectors.

The invention claimed is: 
     
       1. An apparatus for measuring the moisture content of a material, the apparatus including:
 i) an electric field generator and when in use, the material whose moisture content is to be measured is disposed in the electric field and changes in the electric field caused by the material provides a first output that is related to at least two properties of the material, at least one of which is the moisture content and a second property; 
 ii) a temperature sensor for sensing temperature in the electric field and providing a temperature output; 
 iii) a humidity sensor for sensing humidity of the air within the electric field and providing a humidity output; 
 iv) a device that provides a second output that is related to the second property of the material; and 
 v) a processing unit that determines the moisture content of the material with reference to the first output, the second output, and the temperature and humidity outputs. 
 
     
     
       2. The apparatus according to  claim 1 , wherein the second property is the mass of material in or passing through the electric field. 
     
     
       3. The apparatus according to  claim 1 , wherein the apparatus includes a passageway through which the material being measured is conveyed pneumatically or by gravity. 
     
     
       4. The apparatus according to  claim 3 , wherein the electric field extends across the passageway and the first output is based on the changes in the electric field as the material is conveyed through the electric field. 
     
     
       5. The apparatus according to  claim 1 , wherein the device that provides the second output is an optical device that estimates the mass of the material in the electric field. 
     
     
       6. The apparatus according to  claim 5 , wherein the optical device comprises a light source and a light receiver that are arranged such that the material at least in part, is located between the light source and the light receiver and the second output is an output of the light receiver. 
     
     
       7. The apparatus according to  claim 1 , wherein the electric field generator includes a capacitor. 
     
     
       8. The apparatus according to  claim 7 , wherein the capacitor includes at least one pair of capacitor plates arranged opposite and parallel to each other with a space there between, whereby air and the material between the plates provides a dielectric. 
     
     
       9. The apparatus according to  claim 1 , wherein the apparatus further includes a converter that converts either one or a combination of the first and second signals from an analogue signal to a digital signal. 
     
     
       10. The apparatus according to  claim 1 , wherein the apparatus includes output converters adapted to transform the first output and second output into first and second output signals of the same type so that they can be directly compared. 
     
     
       11. The apparatus according to  claim 1 , wherein when the electric field is generated by a capacitor and the first output is a difference in capacitance, the apparatus includes a first converter that converts the first output to a voltage difference signal. 
     
     
       12. The apparatus according to  claim 1 , wherein when the second output is an output of an optical device, the apparatus includes a second converter that converts the second output from the optical device to a voltage signal. 
     
     
       13. The apparatus according to  claim 12 , wherein when the electric field is generated by a capacitor and the first output is a difference in capacitance, the apparatus includes a first converter that converts the first output to a voltage difference signal, and wherein the processing unit calculates the moisture content of the material with reference to: i) the first output signal and the second output signal, or ii) the voltage difference signal of the first converter and voltage signal of the second converter. 
     
     
       14. The apparatus according to  claim 1 , wherein when the electric field is generated by a capacitor and the first output is a difference in capacitance, the apparatus includes a first converter that converts the first output to a voltage difference signal, and wherein when the second output is an output of an optical device, the apparatus includes a second converter that converts the second output from the optical device to a voltage signal, the apparatus including conditioners for adjusting the magnitude of the first and second outputs and/or the voltage difference signal and the voltage signal to enable direct signal comparison. 
     
     
       15. The apparatus according to  claim 1 , wherein the processing unit estimates the relative humidity in the electric field from outputs of the temperature and humidity sensors. 
     
     
       16. The apparatus according to  claim 15 , wherein when the electric field is generated by a capacitor and the first output is a difference in capacitance, the apparatus includes a first converter that converts the first output to a voltage difference signal and when the second output is an output of an optical device, the apparatus includes a second converter that converts the second output from the optical device to a voltage signal, and wherein the processing unit calculates the moisture content as a function that includes variables based on:
 the voltage difference signal of the first converter; 
 the voltage signal of the second converter; and 
 an estimate of the relative humidity in the electric field. 
 
     
     
       17. The apparatus according to  claim 1 , wherein the apparatus includes a flow sensor for sensing the flow rate of air in the electric field. 
     
     
       18. The apparatus according to  claim 1 , wherein the apparatus includes a shield about the electric field to prevent interference from other electromagnetic fields from external sources. 
     
     
       19. A process for determining moisture content of material, the process including the steps of:
 a) introducing material into an electric field; 
 b) measuring changes in the electric field caused by the material introduced into the electric field in step a), wherein the change in electric field relates to the moisture content of the material and another property of the material in the electric field; 
 c) estimating the other property of the material; 
 d) measuring the temperature in the electric field; 
 e) measuring the humidity of the air within the electric field; and 
 f) determining a value for the moisture content using the changes in electric field measured in step b), the other property of the material from step c), and the temperature and humidity measurement from steps d) and e). 
 
     
     
       20. The process according to  claim 19 , wherein the process includes an initial step of generating the electric field. 
     
     
       21. The process according to  claim 19 , wherein step a) involves conveying the material through the electric field pneumatically or by gravity. 
     
     
       22. The process according to  claim 19 , wherein the change in electric field according to step b) relates to at least two properties of the material in the electric field, of which one is the moisture content and another is the mass of the material in the electric field. 
     
     
       23. The process according to  claim 19 , wherein the changes in the electric field are sensed as an output of the electric field generator. 
     
     
       24. The process according to  claim 19 , wherein the electric field is capacitively generated by a capacitor, or inductively generated by an inductor. 
     
     
       25. The process according to  claim 24 , wherein when changes in the electric field are measured by changes in capacitance of a capacitor that generates the electric field, the output of the capacitor is transformed from a capacitance difference into a voltage difference signal. 
     
     
       26. The process according to  claim 19 , wherein estimating the other property of the material according to step c) is based on an output of a device in which the output is representative of mass of the material sensed by the device. 
     
     
       27. The process according to  claim 26 , wherein the device is an optical device that includes a light source and a light receiver, and the output of the optical device is based on amount of light received by the light receiver which is dependent on light transmitted or reflected by the material. 
     
     
       28. The process according to  claim 27 , wherein when the other property of the material is based on the output of the optical device that represents the mass of the material in the electric field, the output of the optical device is transformed into a voltage signal. 
     
     
       29. The process according to  claim 28 , wherein when changes in the electric field are measured by changes in capacitance of a capacitor that generates the electric field, the output of the capacitor is transformed from a capacitance difference into a voltage difference signal, and wherein the magnitude of either one or both of the voltage difference signal and the voltage signal is adjusted to enable direct signal comparison of the voltage difference signal and the voltage signal. 
     
     
       30. The process according to  claim 28 , wherein when changes in the electric field are measured by changes in capacitance of a capacitor that generates the electric field, the output of the capacitor is transformed from a capacitance difference into a voltage difference signal, and wherein step f) includes calculating the moisture content of the material as a function of the voltage difference signal of the capacitor and the voltage signal of the optical device. 
     
     
       31. The process according to  claim 30 , wherein the magnitude of either one or both of the voltage difference signal and the voltage signal is adjusted to enable direct signal comparison of the voltage difference signal and the voltage signal, and wherein step f) includes calculating the moisture content of the material using the formula:
   Moisture= f ( M   cap   ,M   light   ,H,T )+ k    
 
       wherein
 M cap  is the mass indicated by the output of the capacitor such that voltage difference output signal (mentioned above), 
 M light  is the mass indicated by the output of the light sensor such as the voltage signal (mentioned above), 
 H is the humidity, 
 T is the temperature, and 
 k is a constant representative of a number of parameters that will depend on the specific apparatus geometry and sensors. 
 
     
     
       32. The process according to  claim 28 , wherein the process also includes estimating the relative humidity of the air in the electric field using a humidity sensor and the output of a temperature sensor. 
     
     
       33. The process according to  claim 32 , wherein when changes in the electric field are measured by changes in capacitance of a capacitor that generates the electric field, the output of the capacitor is transformed from a capacitance difference into a voltage difference signal, and wherein the magnitude of either one or both of the voltage difference signal and the voltage signal is adjusted to enable direct signal comparison, and wherein step f) includes calculating moisture content of the material in the electric field as function of:
 i) the voltage difference signal of the capacitor; 
 ii) the voltage signal of the optical device; 
 iii) and the relative humidity estimation. 
 
     
     
       34. The process according to  claim 33 , wherein the electric field is of a strength that is suitable for measuring a moisture content up to 16% weight of cotton fiber. 
     
     
       35. The process according to  claim 34 , wherein step f) involves determining the moisture content to an accuracy of ±0.5% weight of water on the weight of cotton fiber. 
     
     
       36. The process according to  claim 26 , wherein the changes in the electric field are sensed as an output of the electric field generator, and wherein the method includes transforming the output of the electric field generator and the output of the device into first and second output signals of the same type so that the output signals can be directly compared. 
     
     
       37. The process according to  claim 19 , wherein step f) is performed using a processing unit. 
     
     
       38. The process according to  claim 19 , wherein the process includes controlling the flow rate of material passing through the electric field. 
     
     
       39. The process according to  claim 19 , wherein the process includes controlling the humidity of the air passing through the electric field. 
     
     
       40. The process according to  claim 19 , wherein the process includes controlling the electric field. 
     
     
       41. An apparatus for measuring the moisture content of a material, the apparatus comprising:
 (i) a capacitor that generates an electric field and when in use, the material whose moisture content is to be measured is disposed in the electric field and changes in the capacitance caused by the material provides a first output that is related to at least two properties of the material, at least one of which is the moisture content and a second property, and a first converter converts the first output to a first voltage difference signal; 
 (ii) a temperature sensor for sensing temperature in the electric field and providing a temperature output; 
 (iii) a humidity sensor for sensing humidity of the air within the electric field and providing a humidity output; 
 (iv) an optical device that provides a second output that is related to the second property of the material, and a second converter converts the second output from the optical device to a second voltage signal; and 
 (v) a processing unit that determines the moisture content of the material with reference to the first voltage difference signal, the second voltage signal, and the temperature and humidity outputs.